this is my prediction, it's mainly based on the hints:

Yamato goes to SHs telling luffy that she wants to join

Luffy refuses, because he doesn't want someone wants to be Oden, he only needs those who want to be themselves

Yamato insists on joining, Luffy uses CoC, so does Yamato, lightning comes out

a clash happens between the two of them, Luffy beats Yamato & sails away from Wano
I think that the scenario I wrote is better than the chapter
 
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